Circuit breaker



Dec. 21, 1948. J. B. MaCNEILL 2,456,971

CIR-SUIT BREAKER Filed Oct. 25, 1944 2 Sheets-Sheet l O m a INVENTOR John; 5. Ma c/Vezll. ATTQRNEYQ WHY m WW ///////v////// a a Dec. 21, 1948.

J.'- B.- M NElLL CIRCUIT BREAKER 2 Sheets-Shed 2 Filed 00);. 25, .1944

ATTORNEY Fig 3.

Patented Dec. 21, 1948 UNITED STATES PATENT OFFICE CIRCUIT BREAKER John B. MacNeill, Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 25, 1944, Serial No. 560,222

7 Claims. 1

This invention relates generally to circuit breakers, and more particularly to circuit breaker operating means.

Circuit breakers employed for the protection of high power circuits encounter varying resistance to operation in different parts of their cycle of operation. Thus, in a circuit opening operation, it is desired that the breaker contacts separate as fast as possible to aid in extinguishing the arc, and for this reason breaker contacts are usually arranged to be tripped open free of the greater part of the contact actuating mechanism, to thereby reduce the mass which need be moved. During a circuit closing operation of circuit breaker contacts, relatively high resistance to movement of the parts is encountered during the final portion of this movement, due to several factors among which are the magnetic forces encountered just at the time contact engagement occurs, and the necessity for establishing the necessary contact pressure in the final closed circuit position. Since the movement of the breaker contacts must be arrested suddenly at the closed circuit position, it is also desirable that the momentum of the moving parts at the end of the closing stroke be relatively small. One,

way of accomplishing this is to var the motive force applied to the moving contact of the breaker so that but a relatively small force is applied during initial closing movement, and a larger force is applied when the resistance to movement 'increases, at the final portion of this movement. Various means have been suggested in the past for varying the force applied to the moving contacts during a circuit closing operation of a circuit breaker, but these generally involve some extraneous means, such as special linkages, throttle valves, and the like.

One object of this invention is to provide novel circuit breaker actuating means which is coordinated with the breaker contacts so as to exert a relatively small force during the first portion of circuit closing movement, and to automatically exert a greater force during the final portion of the circuit closing movement.

Another object of this invention is to provide novel circuit breaker actuating means adapted to exert a variable force on the movable breaker contact during circuit closing movement, but adapted to exert a relatively large and constant force on the moving contact during circuit opening movement thereof.

Another object of this invention is to provide novel fluid motor means for actuating circuit breaker contacts,'so constructed and arranged as to exert a variable force in the movement thereof in one direction.

with the attached drawings, in which:

Figure 1 is a side elevation view of a. circuit breaker embodying this invention, with certain of the parts in section and certain other parts broken away;

Fig. 2 is a side elevation view partially in section of a modified form of circuit breaker embodying this invention; and

Fig. 3 is a longitudinal section view through a modified form of motor adapted to actuate a circuit breaker in accordance with this invention;

Referring to Fig. 101 the drawings the circuit breaker illustrated includes current interrupting means 2,.illustrated schematically as including a' bridging contact 4, preferably composed of a plurality of spring leaves of any suitable resilient conducting material, and adapted to cooperate with a pair ofspaced' flxed contacts 6. The interrupting means 2 maybe of any well known type, as the bridging contact 4 and fixed contacts 6 are shown merely for the purpose of illustrating the position of the parts or the interrupter during operation of a circuit breaker embodying this invention. Bridging contact 4 is adapted to be operated by means of a linkage, schematically illustrated at 8, which connects contact 4 with a breaker operating rod 10. As shown, bridging contact 4 is movable to open the circuit by move- 'ment away from fixed contact 6 under the in fiuence of gravity. and preferably a relatively strong biasing spring (not shown) is also employed to bias bridging contact 4 in a direction to open the circuit.

Contact operating rod l il'is adapted to be connected to a closing motor 40, bymechanism preferably of the type permitting the contact operating rod to trip free of the :motor on a circuit opening operation. Such mechanism may be of any desired type, and that illustrated is similar to that disclosed in J. B. MacNeill et a1. Patent 2,144,502, issued January 17, 1939, and also to the mechanism shown in H. J. Lingal Patent 2,290,977, issued July 28, 1942, both patents being assigned to the assignee of this invention. This mechanism comprises in general a pair of breakerl'evers IZ'between which operating rod I0 is received and pivotally mounted, as by a pivot pin l4, at a point substantially intermediate the ends-orbreakerievejrs l2. Closing levers 11 are provided at each side of breaker levers l2, and are pivotally connected therewith at one end as by a pivot pin I6. Closing levers H are pivotally mounted at their opposite ends on pivot pins 28 mounted on the fabricated frame structure and the adjacent ends of breaker levers l2 are connected by a pin having a latch roller Hi thereon, with the axis of latch roller l8 substantially coinciding with the axis of pivot pins 28. Latch roller 18 on breaker levers I2 is adapted to cooper ate with a latch mechanism 20 to be normally held at the position shown in Fig. 1. At the opposite end of breaker lever 11, pivot pin [6 is also provided with a latch roller 22, and this roller is adapted to cooperate with a latch lever 24 pivotally mounted as at 26 on frame structure 27, to be held by latch lever 24 in the closed circuit position of the breaker. Latch lever 24 is biased in a clockwise direction as viewed in Fig. 1, by a latch spring 30 connected between the latch lever and frame structure 21. Breaker levers l2 are bridged at their ends adjacent pivot pin l6 by a release bar 25, for a purpose to be described. Closing levers H are acted upon by retrieving springs 32 (only one of which. is shown) which react between the respective levers IT and frame structure 21, to bias closing lever l'i ina counterclockwise direction about pivot pins 23, as viewed in Fig. l of the drawing.

Closing levers I! of the trip-free mechanism are adapted to be connected to motor 40 by means of connecting links 36, pivotally connected to the levers as at 34, and adapted to be pivotally connected to the piston rod 38 of the motor 40.

Latch mechanism 20 comprises a latch lever 42 pivotally mounted at 43 on the frame structure, with the movement thereof being controlled by a pair of toggle levers 4'4 and 46. Toggle lever 44 is pivotally connected with latch lever 42 by a pivot pin 50, and toggle lever 46 is pivotally mounted on frame structure 21 by means of a pivot pin 52. are connected by a knee pivot pin 48, and are biased to the right as viewed in Fig. 1 to substantially the position shown where the toggle levers are in a straightened condition,by means of a coil tension spring 54 engaging toggle lever 46 adjacent knee pivot 48.

Toggle lever 46 is provided with a lateral extension 56 adapted to overlie the plunger rod 58 of a trip device 59 also mounted on frame structure 21. Trip device 29 includes a movable core 60 to which plunger rod 58 is attached, and the core is provided in a coil 62 which also has a stationary core part 64.

The breaker is illustrated in Fig. lat the position the parts occupy during a circuit closing operation, just prior to engagement of bridging contact 4 with fixed contacts 6. It will be noted that at this position of the'parts closing levers I1 and breaker levers 12 move together, because breaker levers l2 are held by latch mechanism 20 to pivot about the same axis 28 as closing levers 11. Accordingly, the breaker will be finally closed by continued downward 'movementof motor piston rod 38 and finally cause latch. roller 22 to-be' engaged and held by latch lever 24 at the fully closed position. 4

Now if an overload or other electrical condition occurs which energizes trip coil 62 sufficiently to attract movable core 60 upwardly, the toggle comprising levers 44 and 46 will be broken to the left thus moving latch lever 42 to the left and releasing latch roller [8. This then permits breaker levers l2 to move in a clockwise manner The two toggle levers 44 and 45 4 about pivot pin 16, under the influence of the contact biasing means, to open the circuit free of closing levers i1 and closing motor 4!). During such clockwise movement of breaker levers l2 about pivot pin l6, latch release bar 25 will engage latch lever 24 and move it to the left thus releasing latch roller 22, and permitting retrieving springs 32 to move closing levers H in a counterclockwise manner relative to their pivot 28. Such counterclockwise rotation of closing levers I1 results in counterclockwise rotation of breaker levers l2 about their pivot pin l4 on contact rod H], and this causes latch roller l8 carried by breaker levers l2 to reset beneath latch lever 42. At this point in the operation, the apparatus is conditioned for a circuit closing operation which will occur by operation of motor ill in a manner to move piston rod 33 downwardly. During the circuit closing operation, breaker levers l2 and closing levers i'l move together, as previously explained.

In order to prevent return movement of toggle levers 44 and 46 of latch mechanism 22 to the right, when latch roller I8 is released, a latch blocking lever 98 is provided adapted to automatically hold toggle levers 44 and 46 in the collapsed position to which they are moved by trip device 59, until latch roller 18 on breaker lever l "I is in a position to engage latch lever 42. Latch blocking lever 98 is substantially L-shaped in form, being pivotally mounted on the frame structure as on pivot pin 43, and having an upper edge adapted to be engaged by latch roller I8 when it is in a position to be held by latch lever 42, and the blocking lever has the other end of spring 54 anchored thereto, so as to be biased for rotation about pivot pin 43 in a clockwise direction. Blocking lever 98 has an extension Hi0 adapted to lie just beneath knee pivot 48 of the toggle when latch roller [8 is engaged and held by latch lever 42, but when latch roller I8 is released and the breaker levers l2 move upwardly, blocking lever 98 may move in a clockwise direction a sufficient amount to present the end of extension H10 in a blocking position with respect to knee pivot pin 48.

During a circuit closing operation of the breaker, in moving from the full open position of the contacts to the position shown in Fig. 1, relatively little force is needed to operate bridging contact 4, because there is relatively little opposition to movement of the parts to this position. However, in moving from the position shown in Fig. 1 to the fully closed position, it is not only necessary to stress bridging contact 4 an amount sufiicient to obtain the necessary contact pressure in the closed circuit position, but in closing in on overloads or short circuits, high magnetic forces are also encountered during this final closing movement, and if arcing should occur prior to engagement of the contacts, additional forces will be encountered at this final part of the closing movement. It is not desirable that the force required during this final part of the circuit closing operation be exerted during the initial part of the closing operation, because this would result in a relatively great momentum of the moving parts which would have to be dissipated when the closing operation is completed. Since this would require relatively massive parts or complicated shock absorbing mechanism, it is more desirable that the force exerted during a circuit closing operation .be kept low during the first part of the circuit closing operation, and be automatically increased at the final part of this operation, in order to successfully overcome the relatively large resistances encountered at this point in the operation, without resort to increased 'masses or shock absorbing mechanism.

In accordance with this invention, the force available during a circuit closing operation is automatically controlled by the motor 40. The closing motor 40 may be of the fluid, cylinder and piston type illustrated, with the cylinder including a large diameter portion 66 and a smaller diameter portion 68, and with the piston having a corresponding large diameter portion 10, and small diameter portion I2. The cylinder of the motor is shown as integral with frame structure 21 at its upper end, and has the lower end thereof closed by a cylinder head I4 secured thereto as by bolts I5, with a vent I6 provided in the cylinder head.

' The side wall of the motor cylinder is provided with an inlet opening I8 communicating with a longitudinally extending inlet passage 80 formed in the cylinder wall having at opposite ends thereof an inlet port 82 at the upper end of small diameter portion 68 of the cylinder, and a second inlet port 04 at an intermediate point of the large diameter portion 66 of the cylinder.

Fluid under pressure may be obtained from any desired source such, for example, as a pressure tank 86, which is connected by a conduit 88 with an inlet valve 90, which, in turn, communicates with cylinder inlet I8 by means of a conduit 92. Inlet valve 90 is provided with an operating coil 96,, and is shown in a position to admit fluid to motor 40, with vent 94 in the valve structure being closed.

It will be observed that when the circuit breaker is at its full open position, motor piston I0, I2 will be at the upper end of its travel in cylinder 65, 68 wherein the large diameter portion I of the piston closes inlet port 84, so that when fluid is admitted to the cylinder by energizing coil 06 of the inlet valve, it will be admitted to the cylinder only through inlet port 82.. This means that at the start of the circuit closing operation, fluid under pressure is admitted only to move the small diameter portion I2 of the motor piston. However, when bridging contact 4 reaches the position shown in Fig. l where it is about to engage fixed contact 6. and where a relatively high resistance is encountered in continuing the closing operation to the fully closed position, large diameter portion I0 of the motor piston is beginning to uncover inlet port 84, and thus admit fluid under pressure to the large diameter portion 66 of the cylinder, so that the total force then available to move the piston during this final part of the circuit closing operation is automatically increased by movement of the motor piston itself, and of course this movement is correlated with the movement of bridging contact 4 of the breaker.

It will be observed that after the breaker has attained its fully closed circuit position and coil 96 of the inlet valve is deenergized, this valve may return to its original position under the influence of a biasing spring or the like (not shown), to close off fluid under pressure from conduit 02, and open this conduit to vent 94, so that fluid under pressure within the motor cylinder may escape to the atmosphere. Preferably valve 90 is biased to its lower position, and moved upwardly only when coil 96 is energized.

Fig. 2 illustrates an application of this invention to a circuit breaker utilizing gas under pressure for actuating the breaker contacts to both in arc chute I08..

open and closed positions, and for extinguishing the are formed when the contacts separate. In

this type of breaker, the contacts may be actuated in both directions by the fluid motor, and the device illustrated in Fig. 2 illustrates this type of motor and the way in which a motor constructed in accordance with this invention may be utilized for operating a breaker of this type.

The particular compressed gas breaker illustrated is provided with a gas storage tank I 02 on which is supported a conduit I04 which communicates at its lower end with the storage tank. Conduit. I04 is of an insulating material, and is provided at its point of communication with storage tank I02, with a valve I06 for controlling the flow of gas therethrough. An arc chute I08 is secured to the upper end of conduit I04, and is braced by a bar IIO also connected between the arc chute and storage tank. A stationary contact structure I I2 is adapted to be mounted with The moving contact structure of this circuit breaker comprises a substantially L-shaped contact lever II4 pivotally mounted at II6 on a bracket Ill secured to bar H0 and conduit I04. The outer end of bracket III carries a bumper II8 for limiting opening movement of contact lever H4. The contact lever is adapted to be actuated by a connecting rod I20'of insulating material, which is pivotally connected with an im termediate portion of the contact lever as at I22, and pivotally connected at its other end to a cam plate I24. on a drive shaft I26 suitably mounted in bearings provided on storage tank I02, and the drive shaft is provided with an actuatin crank I28 connected by means of links I30 to the piston rod I32 of a compressed gas motor I34. Cam plate I24 is adapted to cooperate with a cam roller I38 provided on one arm of a bell crank I38, with the other arm thereof connected with the stem of valve I06. A compression spring I40 is provided for urging the valve stem in a direction to cause cam roller I 36 to engage cam plate I24 and to close valve I06.

f lever I I4 into engagement with fixed contact H2,

it is necessary that motor piston rod I 32 be moved further upwardly, and it will be observed that such movement causes cam roller I36 to be received in a notch I25 provided at one end of cam plate I24. When the circuit breaker is actuated to open the circuit, piston rod I32 is moved downwardly causing counterclockwise rotation of shaft I26 and cam plate I24. Initial movement of the camplate causes bell crank I38 to be rotated in a clockwise manner to open blast valve I06 and cause a blast of compressed gas from the storage tank through conduit I04, to be directed through the space between the contacts when they separate. Such movement of cam plate I24 also causes opening of the contacts by means of connecting rod I20.

Since substantially the same high forces are encountered with this breaker during the final part of the circuit closing operation as set forth previously in connection with the breaker illustrated in Fig. 1, it is also desirable that the closing force be relatively small at the start of the closing operation, and that it be automatically increased during such final part thereof. Accordingly, in accordance with this invention, a fluid The cam plate I24 is mountedmotor is provided having a cylinder with a por-' tion I42 of relatively large diameter, and a portion I44 relatively small in diameter. The cylinder has the outer end of the large diameter portion closed by a cylinder head I46, and the lower end of the small diameter portion is seated on a supporting plate I48 which also acts as a cylinder head. The motor piston has a corresponding large diameter portion I50 and small diameter portion I52. A supply conduit I54 is provided from storage tank I02, with electromagnetically operated valves I56 and I58, respectively, controlling the admission of gas to opposite ends of the motor cylinder. Thus, valve I56 controls the admission of gas from supply conduit I54 to a pipe I60 leading to an inlet port at the upper end of the large diameter portion I42 of the cylinder, and valve I58 controls the admission of fluid from supply conduit I54 to a longitudinally extending inlet passage I62 formed in the side wall of the motor cylinder. This inlet passage I62 is provided with a bottom inlet port I64 at the lower end of small diameter portion I44 of the cylinder, and with an intermediate inlet port I66 located intermediate the ends of the large diameter portion I42 of the cylinder. Valves I56 and I58 may be of any desired type, preferably of a type adapted to admit fluid under pressure to the motor cylinder in one position, and in another position to vent the cylinder to atmosphere, like the valve 60 shown in Fig. 1.

In the operation of the motor structure shown in Fig. 2, during a circuit closing operation starting from the point where the motor piston is at its lowermost position, and the breaker contact lever is at its open position wherein it is in engagement with bumper II8, it will be observed that operation of valve I58 to admit fluid to inlet passage I62 results in fluid being admitted to the cylinder solely through port I64, because port I66 will be closed by the large diameter portion I50 of the motor piston. This results in a relatively small force applied to the motor piston during the first part of the circuit closing operation, until the motor and contact lever I I4 reach the position shown in Fig. 2, just prior to engagement of contact lever II4 with fixed contact structure II2. At this point the large diameter portion I50 of the motor piston starts to uncover port I66, thus admitting fluid pressure to the large diameter portion I42 of the cylinder, thereby increasing the force exerted by the motor on contact lever II4 during this final portion of the circuit closing operation.

When it is desired to operate the circuit breaker to open the circuit, valve I56 is energized to admit fluid under pressure to the upper portion of the motor cylinder, and since it is highly desirable that the circuit opening operation take place at as high a speed as possible in order to obtain efficient and fast arc extinction, it will be observed that this is accomplished by motor I34, because the compressed gas is admitted to the large diameter portion I42 of the cylinder, thus operating on the large diameter portion I50 of the piston to exert the maximum force which the motor is capable of on the contact lever II4 during a circuit interrupting operation. It will thus be observed that during a circuit opening operation the maximum force of the motor is utilized to obtain rapid opening of the breaker contacts and consequently the most efiicient circuit interruption characteristics. However, during a circuit closing operation but a small force is exerted during the first part of the movement of contact lever II4 towards fixed contact structure H2, and a much greater force is automatically exerted during the final part of this operation when relatively high mechanical resistance is encountered.

Fig. 3 of the drawings illustrates a modified form of motor capable of use for operating a circuit breaker during the circuit closing operation with a variable force in substantially the same manner as the fluid motors described and illustrated in Figs. 1 and 2 of the drawings. The particular motor I68 illustrated in Fig. 3 comprises a cylinder having a large diameter portion I10 and a smaller diameter portion I12. There Is provided within the motor cylinder a piston structure having a corresponding large diameter portion I14, and a small diameter portion I16. A fluid inlet port I10 is provided solely at the lower end of small diameter portion I12 of the cylinder, and in this particular instance, a vent I is provided at the upper end of the large diameter portion I10 oi the cylinder. The motor piston is provided with an integral piston rod I82 projecting through the upper end of the cylinder to be connected with a breaker operating rod I84.

The motor I68 is arranged so that upward movement thereof, as viewed in Fig. 3, will cause a circuit closing operation. It will be observed then, that when fluid is admitted to inlet port I18, it will act only on the small diameter portion I16 oi the motor piston. Accordingly, the first portion of the closing movement of a breaker operated thereby will not be excessively fast. However, as soon as the motor piston has moved an amount sufficient to cause the small diameter portion I16 to enter the flared upper end of the small diameter portion I12 of the cylinder, fluid under pressure will then be admitted to the large diameter portion I10 of the cylinder, and will act on the large diameter portion I14 of the piston, and thereby automatically increase the force available during the final portion of the circuit closing operation of a breaker operated thereby.

From the foregoing, it will be apparent that this invention provides a novel circuit breaker construction, having actuating means coordinated with the breaker contacts in a manner such that a relatively small force is exerted by the actuating means during the first portion of a circuit closing operation, and this force is automatically increased during the final part of the circuit closing movement to overcome the relatively large resistance encountered during this portion of the operation. Moreover, this is accomplished in a relatively simple manner with no moving parts or additional controls than those now employed in fluid operated breakers. Moreover, where the breaker may be operated to both open and closed circuit positions by the entire operating mechanism, the arrangement of this invention provides a circuit closing operation as described above, and a circuit opening operation where the full force which the operating means is capable of is exerted on the moving contact to obtain rapid opening of the contacts and consequent efficient and rapid arc extinguishment.

Having described preferred embodiments of the invention in accordance with the patent statutes, it is desired that the invention be not limited to these particular structures, inasmuch as it will be apparent to persons skilled in the art that many modifications and changes may be made in these particular structures without 9 departing from the broad spirit and scope of this invention. Accordingly, it is desired that the invention be interpreted as broadly as possible, and that it be limited only as required by the prior art.

I claim as my invention:

1. A circuit breaker comprising, separable contact means at least one of which is movable into and out of engagement with the other, fluid motor means for at least actuating said movablecontact means in a direction to engage the other of said contact means, actuating mechanism connecting said motor means and movable contact for transmitting movement of said motor means to said contact means to close the breaker, means comprising a part of said motor means independent of said mechanism, which is operable to automatically increase the force exerted by said motor means during the final part of a circuit closing operation in response to closing movement of said motor means an amount sufficient to actuate said movable contact-means fromits open circuit position spaced-away from the other of said contact meansto-a position iii-proximity motor means comprising a cylinder and piston 11- one of which is movable and operatively connected with said actuating mechanism, said piston and cylinder having corresponding stepped portions differing in cross section area, means for admitting fluid under pressure to the cylinder portion of smal cross section area to initiate circuit closing movement of said movable contact, and means responsive to circuit closing operation of said motor means an amount suflicient to actuate said movable contact means from its open circuit position spaced away from the other of said contact means to a position in proximity to but still spaced from said other contact means for automatically admitting said fluid under pressure to the cylinder portion of larger cross section to thereby increase the closing force transmitted to said contact means during the latter part of contact closing movement, and the last mentioned means including a fluid inlet for said large cylinder portion which is separate and independent of the fluid inlet for the small cylinder portion.

3. In a circuit breaker, separable contact means at least one of which is movable into and out of engagement with the other, fluid motor means for at least actuating said movable contact means in a direction to engage the other of said contact means, actuating mechanism connecting said motor means and movable contact for transmitting movement of said motor means to said contact means to close the breaker, said motor means comprising a cylinder and piston one of which is movable and" operatiavely connected with said actuating mechanism, said piston and cylinder having corresponding portions difiering in cross section area, means for admitting a fluid under 7 pressure to said cylinder communicating with a port for each of said cylinder portions, the port for said cylinder portion of large cross section being covered by said piston when said movable breaker contact means is at its full open circuit T5 motor means independent of said mechanism,

i 7 position, and is uncovered only in response to relativemovem'entoi said piston and cylinder an amount 'sumcient to actuate said movable contact meansirom its full open position to a posi- 1 .tion in proximity to theother of said contacts to thereby increase the closing force transmitted to 'said' contact means during the latter part of contact closing rnov'en' ent.

14. In a circuit breaker, separable contact means in ,atileast one oiwhich is movable into and out of engagement with the other, fluid motor means for at least actuating said movable contact means in ga'fdirection to engage the other of said contact frneans; actuating j mechanism connecting said motor means and movable contact for transmitting movement ofsaid motor means tosaid contact means'to close the breaker, said motor means comprising a cylinder and piston one of which is 'movable'and op erativeiy connected with said ac- 'tuating mechanism, said piston and cylinder hav- 'movabiecontact',and said piston and, cylinder "portions oi smailjcross'section both being shorter 'thanthe' travel of saiiipiston so that said small 'pist onportion is movable during a circuit closin operation out of said cylinder portion of small in) cross section to admit said fluid directly to the cylinder portion of large cross section by relative movement of said piston and cylinder from the full open position of said breaker an amount sufflcient to actuate said movable contact means to a position in proximity with the other of said contact means to thereby increase the closing force transmitted to said contact means during the latter part of contact closing movement.

5. In a circuit breaker, separable contact means in at least one of which is movable into and out of engagement with the other, fluid motor means for actuating said movable contact means, actuating mechanism connecting said motor means and movable contact for transmitting movement of said motor means to said contact means to close the breaker, said motor means comprising a cylinder and piston one of which is movable and operatively connected with said actuating mechanism, said piston and cylinder having corresponding portions differing in cross section area,

means for admitting fluid under pressure to the cylinder portion of small cross section area to initiate circuit closing movement of said movable contact, means responsive to circuit closing operation of said motor means an amount sufil- 0 under pressure to the cylinder portion of larger 0 actuating said movable contact means, actuating mechanism connecting said motor means and movable contact for transmitting movement of said motor means to said contact means to close the breaken'means comprising a part of said which is operable to automatically increase the force exerted by said motor means during the final part of a circuit closing operation in response to closing movement of said motor means an amount sufficient to actuate said movable contact means from its open circuit position spaced away from the other of said contact means to a position in proximity thereto, and means for causing said motor means to exert said greater force to separate said contact means to efiect a circuit opening operation at a relatively high rate of speed.

'7. In a circuit breaker, separable contact means at least one of which is movable into and out of engagement with the other, fluid motor means for at least actuating said movable contact means in a direction to engage the other of said contact means, actuating mechanism connecting said motor means and movable contact for transmitting movement of said motormeans to said contact means to close the breaker, said motor means comprising a cylinder and piston one of which is movable and operatively connected with said actuating mechanism, said piston and cylinder having corresponding portions differing in cross section area, means for admitting a fluid under pressure to said cylinder communicating with a port for each of said cylinder portions, the port for REFERENCES CITED The following references are of record in the file of this patent:

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